The origins of hyperbaric medicine go back to the long-standing sciences of diving. Seeing that the general concept of diving pivots around the idea of using compressed gases in order to allow humans to survive underwater, a lot of the technologies and methods used in modern HBOT are derived from this ancient science.
Diving is recognized as far back as 4500 B.C. when individuals who made their living as mother-of-pearl divers were able to hold their breath for extended periods of time. These first “free divers” experienced an increased lung capacity the deeper they went. As a result, they experienced the first cases of decompression illness.
Xerxes, king of the Persian Empire in 400 B.C., used free divers to salvage sunken goods and treasures from ships he had conquered at sea. Some of these dives were recorded as being 20 to 30 meters and taking up to 4 minutes. In 320 B.C., Alexander the Great was rumored to be the first to use diving equipment when he was lowered into the Bosphorus Straits in a glass case during his siege on the island of Tyre. This was supposed to have given him a strategic advantage to find any weaknesses in the island’s defenses, since walls surrounded the island at the sea.
During the Italian Renaissance, Leonardo da Vinci made numerous sketches of what could have become diving devices. However, as far as we know, none of them were ever produced or experimented with.
The first true diving bell was invented in 1620 by a Dutchman named Cornelius Drebbel. Bell’s invention had an open bottom and relied on the pressure of the water to keep air trapped within the bell. The device was lowered into the water by crane and relied on a ballast to keep the structure properly oriented. Pump-fed hoses would provide the occupants of the bell with fresh air while excess gases would leak out from under the lip of the bell. The deeper the bell went the more gas would need to be provided to keep the occupants comfortable. While it was never meant to move under the control of divers within the bell, the design allowed Drebbel’s bell to serve as a base of operations for free divers.
In 1687, Sir William Phipps used an inverted container to recover nearly 200,000 English pounds of sterling treasure from a chest off the coast of San Domingo. The perpetual prankster and famous surrealist Salvador Dali would frequently show up to speaking engagements enclosed in a diving bell and would insist on speaking from inside of it.11
In the natural world there is the diving bell spider. Feeding on mostly underwater prey, the spider must create a diving bell in order to breathe air while it waits for its next meal. In order to do so it creates a bell from silk and attaches it to an underwater plant. The spider then collects air in the dense hairs on its abdomen and legs and transports it to the bell to replenish the supply.
The Diving Bell Spider, also called the Water Spider, lives entirely under water. This species is found in Northern and Central Europe, northern Asia, and in Africa north of the Sahara desert. The spider does breathe air, which it traps in the hairs on its abdomen and legs and takes down to its “diving bell.” Here it lives except when it needs to surface for more air, or when it hunts underwater prey.
The structure of the bell allows gas-exchange with the surrounding water. Carbon dioxide is expelled and oxygen is replenished, to some extent, due to osmotic pressure. This system has been called the “aqua-lung” of the Water Spider, but it is actually significantly more sophisticated than any human-made aqua-lung.12
Expanding on the idea of a diving bell are moon pool-equipped habitats. Moon pools are used on long-term underwater facilities that allow divers to spend time in dry comfort while still being acclimated to the increased underwater pressure. By removing the need to continually return to the surface, the risk for nitrogen entering the bloodstream (known as “the bends” or “caisson disease”) is greatly diminished. The bends typically occurs when the air pressure is greater than 1.6 standard atmospheres, which typically corresponds to a depth of 6 meters (20 feet).
Commercial diving operators now commonly use hyperbaric chambers in their work. The seal-able diving chamber uses an air pump rather than ambient water pressure to dictate the internal air pressure. This allows for a huge safety advantage as it can allow decompression to be done after the vessel is well above the surface of the water. This is especially vital for saturation divers and undersea rescue operations.
Although they may make diving significantly safer, operating the sealed diving chambers is still a dangerous game in itself. Pressure between the interior and exterior of the chamber usually differs greatly and as a result several fatal accidents have happened. Because of this, the design, manufacturing and operation of sealed diving chambers and hyperbaric chambers is done by federally regulated and certified engineering authorities.
While the government regulatory authorities vary from country to country, all of them enforce the maximum standards when it comes to operation and temperature parameters of the chambers. Such regulatory committees include the ASME Boiler and Pressure Vessel Code in North America, the Pressure Equipment Directive of the EU (PED), the Japanese Industrial Standard (JIS), the CSA B51 in Canada, the AS1210 in Australia and other international standards like Lloyd’s, Germanischer Lloyd, Det Norske Veritas, and the Societe Generale de Surveillance (SGS S.A) Stoomwezen.
12Norman I. Platnick (27.3.2010). “Fam. Cybaeidae Banks, 1892d: 95” The World Spider Catalog, Version 11.0. American Museum of Natural History.